In the prior art stand tube of a bicycle, a front tube is connected to a stand tube. However in this prior art, the front tube is not adjustable to the stand tube in many different orientations.
In one prior art, the Taiwan Patent No. 570010, an improvement structure is disclosed.
In the prior art, a straight retainer and a transversal rod are used. One side of the straight retainer has a C shape mouth. A slit is formed in an opening of the mouth. A center of the mouth is hollowed. Two sides of the hollow portion are formed with angled holes. One end of the transversal rod has a slot for mounting the mouth. Two sides of the slot are wings. An outer end of the wing has a teeth surface for adhering a first block and a second block which have teeth rings. Each teeth ring has an angled end which can be inserted into the angled hole and then be clamped by the C shape mouth. Studs pass through the first and second blocks and the wings and elastic elements pass through the angled holes so that the first and second blocks tightly retains the teeth surfaces. By the angled holes and the angled ends, the transversal rod will not rotate and the gaps disappear.
Furthermore, in this stand tube, by the studs, the teeth rings of the first and second blocks and the teeth surfaces are tightly combined. Thereby positioning therebetween is adjustable effectively. When the stud is released, the blocks and the teeth surfaces will separate from one another. The transversal rod is movable and is adjustable along the angled ends.
However the prior art has the following disadvantages.
The straight retainer has a C shape mouth and a slit. Furthermore, the locking holes and angled holes are formed longitudinally and transversally. Thereby the straight retainer has a weak structure.
In assembly, in this stand tube, by the studs, the teeth rings of the first and second blocks and the teeth surfaces are tightly combined. Thereby positioning therebetween is adjustable effectively. However the shoulders of the first and second blocks resist against the penetrating hole and the angled ends are received into the angled holes of the straight retainer. The teeth rings are adhered to the tooth surfaces. The installation is not formed with a firm and rigid structure. If the structure is used for a long time, the angled ends will release, while the user is seldom to find this phenomenon and thus it will hurt the users.
Moreover if the screw cannot effectively lock the C shape mouth, the C shape cannot provide an effective pressing force and thus gaps generate. This will induce some dangerous conditions when the bicycle moves forwards. It is possible that the bicycle is out of control.